This invention relates to a rotary stamp. More particularly, the present invention relates to a rotary stamp which comprises an inverted U-shaped frame comprising of a top plate and right and left side plates, each having an opening formed substantially at the center and a slit at the lower end thereof; a shaft inserted into the openings; a bridge mounted between the slits; cylinder means rotatably fitted over the outer circumference of the shaft at the portion positioned inside the frame; operation means for rotating the cylinder means; and endless belt-like stamping means mounted around the cylinder means and the bridge, having a number of character portions on the upper surface thereof and made of an elastic material.
A known rotary stamp representing an improvement over the abovementioned rotary stamp comprises an inverted U-shaped frame consisting of a top plate and right and left side plates, each having an opening formed substantially at the center, a further opening below said opening and a slit at the lower end thereof; a shaft inserted into the upper openings, spring means inserted into said lower openings; a bridge mounted between the slits and having a recess at the lower end thereof; cylinder means rotatably fitted over the outer circumference of the shaft at the portion positioned inside the frame; operation means for rotating the cylinder means; an ink-adsorbing member incorporated in said recess; endless belt-like stamping means mounted around the cylinder means and the ink-absorbing member, made of a porous elastic material and having a number of character portions formed on the upper surface thereof; covers for covering the front and back portions of the frame, respectively; and a cap so disposed as to be capable of moving up and down along the side plates of the frame and the outer surfaces at the lower portions of the covers, and having an opening at the lower portion thereof; the spring means normally pushing the cap downwardly so that the surface of one of the character portions is pulled into the cap when said one character portion reaches the lowermost position due to the rotation of the operation means, and allowing the surface of said one character portion to protrude outwardly from the opening of the cap thereby to effect stamping when the cap is pressed down on an article to be stamped against the force of the spring means.
Rotary stamps for stamping the date of the above-mentioned kind are disclosed in, for example, U.S. Pat. Nos. 4,033,257 and 4,038,918 (granted to Takaji Funahashi on July 5, 1977 and Aug. 2, 1977, respectively). According to these disclosures, the above-mentioned endless belt-like stamping means consists of a large number of stamping units, and the cylinder means, on which these stamping units are to be mounted individually, are required to be the same in number as that of the stamping units. Furthermore, the same number of operation means are required in order to rotate these numerous cylinder means. In the rotary stamp for stamping the data of this kind, each of the operation means is inevitably composed of a thin disc having gears around its circumference in view of the size of the rotary stamp as a whole. Accordingly, if the endless belt-like stamping means has a large width, the rotational force of the thin discs is likely to insufficient for rotating the stamping means.
In particular, when the endless belt-like stamping means is formed as a unitary structure of a large width, it is impossible to rotate this structure in its entirety by the same amount using one operation means. This results in deformation of the stamping means and hence, deformation of the stamped characters. It is not easy to rotate the endless belt-like stamping means simultaneously by the same amount, even if the operation means are disposed at both end portions of the cylinder means.